Sasha Mordovets/Getty Images(BRUSSELS, Belgium) -- A shift in favor of Syria’s opposition could be on the horizon in the country’s civil war, according to a U.S. official, but President Bashar al-Assad is not likely to leave anytime soon.

The armed opposition is making important tactical gains that could eventually trigger a strategic shift in the conflict, the official told ABC News Wednesday, adding that pressure on the regime is mounting and Assad’s forces are having difficulty beating back insurgent gains.

“Assad’s levers of influence are fraying and his reach is contracting, but the regime core is a tough nut that doesn’t seem to be cracking just yet,” the official said. “Although pressure is mounting, it’s difficult to say when the breaking point will come, because there’s little to suggest that Assad is a cut-and-run kind of guy.”

The U.S. official said the opposition is better supplied than in the past, but competition for resources is complicating their efforts.

“Factional infighting is clearly something the opposition has to guard against to be successful,” the official said.

“It’s a great tribute to NATO that this decision to deploy patriots was taken, because it’s very much in line with the solidarity of our members. This is for defensive purposes, that’s made absolutely clear in the statement that was agreed upon. It is solely for the defense of Turkey,” Sec. Clinton said at a news conference in Brussels Wednesday. “I don’t believe that it necessarily brings any greater attention to the tragedy unfolding in Syria, but it does send a clear message to the Syrians that Turkey has the full support of it’s NATO allies.”

Late last week, U.S. intelligence found the Assad regime had taken preparatory steps with regards to some its chemical weapons supply.

Clinton condemned the use of chemical weapons in Syria, calling it a “red line” for the United States for a second time.

“We’ve made our views absolutely clear,” Clinton said. “Our concerns are that an increasingly desperate Assad regime might turn to chemical weapons or might lose control of them to one of the many groups now operating within Syria. As part of the absolute unity we all have on this issue we have sent an unmistakable message that this would be a red line and those responsible will be held to account.”

President Obama has said use of such weapons could trigger a response from the United States.

“The use of chemical weapons is and would be totally unacceptable,” Obama said Monday. “And if you make the tragic mistake of using these weapons, there will be consequences, and you will be held accountable.”

Following Clinton’s press conference in Brussels Wednesday, the State Department announced she will travel to three Middle Eastern countries next week. Her first stop will be in Morocco for a Friends of Syria meeting, the success of which, she said, depends on Assad’s willingness to cooperate.

“I’m looking forward to the Friends of the Syrian People meeting next week where we will explore with like-minded countries what more we can do to bring this conflict to an end,” Clinton said, “but that would require the Assad regime making the decision to participate in a political transition, ending the violence against its own people. And we hope they do so because we believe their fall inevitable. It’s just how question of how many people will die until that day occurs.”